As these examples show, there are a few different schools of thought as to what app-vertising should look like. But the industry has some time to figure things out — right now it isn't a completely mass medium. Noah Elkin , principal analyst with eMarketer , says that if you're releasing a mobile app designed to be used on a smartphone, you're effectively writing off 70% of the market. Though some predict that the user base for smartphones will hit 50% of consumers by the end of this year, Elkin says that figure is too optimistic. It's also worth noting that early adopters to smartphones may be more engageable than those who buy them a year or so from now.